This disclosure relates to a semiconductor device and more particularly, to a semiconductor device for detecting degradation of a semiconductor element caused by hot carrier.
In these days, semiconductor devices are being highly integrated according to a development in a micro-processing technology. A power voltage system, however, does not achieve a low voltage operation according to the miniaturization of the semiconductor devices. Therefore, field intensities of internal elements forming a semiconductor device tend to increase. Especially, in a Metal-Oxide-Semiconductor (MOS) transistor, there occurs a hot carrier phenomenon that hot carrier (hereinafter, also referred to as HCI) caused by an increase of the field intensity is injected in a gate insulation film. This hot carrier phenomenon degrades (increases) the threshold voltage of the MOS transistor.
With respect to the degradation detection of a semiconductor element, for example, Japanese Unexamined Patent Application Publication No. 2011-47733 discloses a circuit for estimating a degradation degree of a transistor in a small sized circuit. Specifically, the technique disclosed in this patent publication is to provide a circuit having a resistance between a transistor to be estimated and a power supply, for estimating the degradation of resistance divided voltage property according to the divided resistance voltage.
Japanese Unexamined Patent Application Publication No. Hei 5(1993)-157799 discloses a detection circuit of degradation of a semiconductor element by HCI. Specifically, the technique disclosed in this patent publication is to eliminate influence on an electrode terminal for estimating direct current electric characteristic and apply an alternating current stress closer to the actual circuit operation, to a transistor to be estimated.
Japanese Unexamined Patent Application Publication No. Hei 11(1999)-118874 discloses a circuit for detecting HCI degradation of a MOS transistor using a ring oscillator. Specifically, the technique disclosed in this patent publication is to detect HCI degradation by enlarging the fluctuation of oscillation frequency in a ring oscillator according to a boosting circuit.